This invention relates to devices for driving piping sections through ground, and in particular for installing tubular piping or conduits beneath highways and other hard surfaces.
Generally, the most convenient method for installing piping, cable or the like under ground is to form a trench along a predetermined path, install the piping or cable and refill the trench. This approach can be time consuming and difficult in connection with installations under particularly hard surfaces, for example highways, streets, sidewalks, parking lots and airport runways. In such applications, it is preferable to install pipe or cable without a breaking of the ground above and the subsequent need to repair the surface.
One known approach to meeting this need involves digging a working trench on one side of the hard surface, e.g. a highway. An underground pipe installing device is anchored within the trench, oriented to support and drive a pipe installing rod horizontally into the ground beneath the highway. The rod is advanced or driven through the ground, for example by one or more hydraulic cylinders, until the lead end of the rod emerges on the opposite side of the highway, e.g. into a target trench previously formed on the opposite side.
In certain pipe installing devices, pipe sections themselves are used in lieu of the pipe installing rod. For example, U.S. Pat. No. 3,347,521 (Bingham) is directed to a device which drives a tubular metal conduit. At the lead end of the conduit is a rounded drive head provided with an adapter section to accommodate different conduit diameters. A second adapter is provided for attaching the rearward end of the conduit section to the plunger of a hydraulic ram.
U.S. Pat. No. 3,834,668 (Casey) discloses a pipe pushing apparatus employing two hydraulic cylinders, one on each side of the pipe section being driven. Ground abutting end plates at opposite ends of the device secure it with respect to the ground. Pivotally mounted jaws on opposite sides of the pipe sections are movable to grip the pipe for alternatively and selectively pushing or pulling the pipe, depending on which members of a set of removable pins are installed. Forwardly of the jaws is a guide for orienting and stabilizing the pipe section. U.S. Pat. No. 3,952,384 (Goldry et al) shows a set of three jaws, surrounding a pipe and spaced apart from one another 120 .degree..
U.S. Pat. No. 4,455,107 (Schosek) concerns a device for installing a solid cylindrical rod in which opposite jaws have semicircular profiles generally conforming to the circular profile of the rod. The opposed jaws are interconnected through motion transmitting devices, said to ensure equal gripping of the opposed jaws so that no flow divider is needed in connection with the hydraulic fluid drive system.
Due to the high forces involved, sometimes up to sixty tons on the jaws or other pipe gripping members, a secure, properly centered gripping action is critical. The proceeding patents are directed to various methods of gripping the piping section or rod for driving. These approaches, while satisfactory in certain respects, fail to address the need to ensure repeated, properly centered gripping of pipe or rod sections by hydraulically reciprocated jaws.
Therefore, it is an object of the present invention to provide a hydraulic pipe driving apparatus with means for biasing pipe gripping jaws into closure prior to initiating a forward stroke of the jaws.
Another object of the invention is to provide a pipe driving apparatus with interchangeable jaw inserts corresponding to pipes of different sizes, as well as interchangeable inserts for pipe guiding structure spaced apart from the jaws.
Another object of the invention is to provide an improved means for centering a driven rod or pipe with respect to opposed jaws or other gripping members.
Yet another object is to provide a means for closing opposed, hydraulically operated jaws or other gripping members upon a pipe or rod, operable independently of the forward driving action of the hydraulic cylinders.